Ocular Motor Nerves Visual Pathways – Neuroanatomy – for grade III medical students 蔡子同 成大醫院神經科 2012/05/09

Visual System -- Afferent and Efferent -- Afferent Visual System Retina (ganglion cell axons), Optic nerve, Optic chiasm, Optic tract, Lateral geniculate nucleus (thalamic relay nucleus), Optic radiation, Visual cortex (occipital lobe) Efferent Visual System Extraocular muscles Cranial nerves Supranuclear pathways Ocular Autonomic Pathways Sympathetic pathway Parasympathetic pathway

Cranial Nerves II Optic nerve III Oculomotor nerve IV Trochlear nerve VI Abducens nerve

Manifestations of the Visual System Dysfunction Afferent Visual System Visual loss (loss of visual acuity) Visual field defect Efferent Visual System Diplopia (double vision) Gaze palsy Ptosis (blepharoptosis) Ocular Autonomic Pathways Anisocoria (unequal pupil size) Mild ptosis

Visual System -- Afferent and Efferent -- Afferent Visual System Retina (ganglion cell axons), Optic nerve, Optic chiasm, Optic tract, Lateral geniculate nucleus (thalamic relay nucleus), Optic radiation, Visual cortex (occipital lobe) Efferent Visual System Extraocular muscles Cranial nerves Supranuclear pathways Ocular Autonomic Pathways Sympathetic pathway Parasympathetic pathway

Eye Ball; Retina; Fundus

Retina

Cellular Organization of the Retina Cell Layer Neuronal and Glial Nuclei Outer nuclear layer • Photoreceptors (rod; cone) Inner nuclear layer • Horizontal cells • Bipolar cells • Interplexiform cells • Amacrine cells • Müller cells Ganglion cell layer • Ganglion cells • Displaced amacrine cells • Astrocytes Miller NR et al (eds): Walsh & Hoyt's Clinical Neuro-Ophthalmology: The Essentials, 2nd ed, 2008. Chapter 2, pp 43

Visual Pathway

Visual Field Confrontation test

*** Visual Pathways

Visual Pathways

*** Visual Field Defects Localization

Visual System -- Afferent and Efferent -- Afferent Visual System Retina, Optic nerve, Optic chiasm, Optic tract, Optic radiation, Cortex Efferent Visual System Extraocular muscles Cranial nerves Supranuclear pathways Ocular Autonomic Pathways Sympathetic pathway Parasympathetic pathway

*** Extrinsic Ocular Muscles Superior view Anterior view Right lateral view

Actions of the Extraocular Muscles -- with the Eye in Central Position -- Cranial nerve Primary action Secondary action Tertiary action Medial rectus III Adduction -- Superior rectus Elevation Intortion Inferior rectus Depression Extortion Inferior oblique Extorsion Abduction Superior oblique IV Intorsion Lateral rectus VI

Origins of the Ocular Motor Nerves - Sagittal & transverse sections of the Brainstem -

Ocular Motor Nerves Schuenke M et al. Thieme Atlas of Anatomy- Head and Neuroanatomy, Thieme, 2007

Oculomotor Control - Final Common Pathway -

Conjugate Eye Movement-- Gaze

Purposes of Eye Movements Purpose of eye movements to place and maintain the image of regard on the foveas Classification of eye movements saccade smooth pursuit vestibuloocular reflex optokinetic response vergence

Pathways between Semicircular Canals and Eye Muscles in the Cat Stimulation Inhibition

Pathways of Saccade- Horizontal Gaze

Ocular Motor Control System INC III MLF Vestibular nucleus PPRF

Visual System -- Afferent and Efferent -- Afferent Visual System Retina, Optic nerve, Optic chiasm, Optic tract, Optic radiation, Cortex Efferent Visual System Extraocular muscles Cranial nerves Supranuclear pathways Ocular Autonomic Pathways Sympathetic pathway Parasympathetic pathway

*** Pupillary Light Reflex -- Sympathetic & parasympathetic pathways --

*** Intrinsic Ocular Muscles Ciliary muscles (parasympathetic) When the ciliary muscle contracts, it pulls the choroid forward and relaxes the zonular fibers. As these fibers become lax, the intrinsic resilience of the lens causes it to assume the more convex relaxed shape. Pupillary sphinctor (parasympathetic) an anular muscle contraction of the muscle constricts the pupil Pupillary dilator (sympathetic) radially disposed contraction of the muscle dilates the pupil Schuenke M et al. Thieme Atlas of Anatomy- Head and Neuroanatomy, Thieme, 2007

Pupillary Abnormality

Pupillary Light Reflex and Accommodation Reaction Light reflex– The afferent pathway is the optic nerve and tract, from the retina to the pretectal region of the midbrain. The efferent pathway is in the oculomotor nerve: parasympathetic fibers from the accessory oculomotor nucleus (E-W nucleus), synapsing in the ciliary ganglion, and supplying the sphincter pupillae. Because of contralateral connections, exposure of only one eye to light causes constriction of both pupils (consensual light reflex). Accommodation reaction– The afferent pathway extends from the retina to the visual cortex, and then to the pretectal region. The efferent pathway, similar to that of the light reflex, ends in the ciliary muscle (accommodation for focusing on near objects), sphincter pupillae (miosis), and medial rectus (convergence of the eyes).

Levator Palpebrae Superioris; Superior Tarsal Muscle (or Müller’s Muscle) Schuenke M et al. Thieme Atlas of Anatomy- Head and Neuroanatomy, Thieme, 2007